Field of the Invention
The present invention relates to a mirror surface measuring apparatus which can be used to measure, for example, an inclination angle and/or a position, etc., of a reflection surface of a movable mirror in a single lens reflex camera.
Description of Related Art
In a conventional view finder of a single lens reflex camera, the light flux of an object transmitted through the taking lens is reflected by a movable mirror, such as a quick return mirror, toward a finder optical system, so that an object image can be formed on a screen lying in a plane which is spaced from the mirror at the same distance as the film plane but orthogonal thereto. The object image on the screen is observed through a pentagonal prism and an eyepiece.
If the inclination angle of the movable mirror does not meet an intended design value, the object image will be distorted or partially out of focus, or parallax might occur in which the range of the image in the finder might not be identical to the range of an actual object image exposed on the film. Furthermore, parallax error can also occur when the position of the movable mirror in the optical axis direction is deviated from a predetermined design value. To avoid these problems, it is necessary to measure or detect the inclination angle and the axial position of the movable mirror, upon assembly thereof.
The significant requirements needed to measure the inclination angle and the axial position of the movable mirror are 1 non-contact measurement, 2 quick measurement, and 3 selection of simultaneous or independent measurement of the angle and the position, etc.
Among the known measuring methods are the contact-probe method, the microscope method, and the auto-collimating method. In the contact-probe method, since a probe is brought into contact with a mirror to be measured, the mirror can be damaged. Furthermore, the measurement and adjustment can not be effected simultaneously.
A major disadvantage of the microscope method is that it requires a long time to complete the measurement. In the auto-collimating method, the detection of the position cannot be carried out while the angle is being detected.